The present invention relates to a ferrochromium slag which is intended for uses requiring refractoriness and resistance to mechanical pressure and wear, e.g. for use as blasting sand or as an aggregate in cast concrete, asphalt or bricks.
U.S. Pat. No. 3,798,043 discloses a method of preparing refractory concrete from the slags of ferrochromium production. The ferrochromium slag used contained 25-40% MgO, 20-50% SiO.sub.2, 10-40% Al.sub.2 O.sub.3 and less than 15% by weight Cr, Cr.sub.2 O.sub.3, CaO, FeO, C and S. Classified ferrochromium slag was blended with the calcium aluminate cement used as the cementing agent and with water, and possibly with ground boron phosphate serving as a fluxing agent. The ratio of cement to slag was 1:4, and a castable blend was obtained by adding so large a quantity of water that the ratio of water to cement was 0.6. Finally the castings were heat treated at a temperature above 1000.degree. C.
The object of the present invention is to provide a slag of ferrochromium production which is usable for purposes in which it is subjected to fire and to mechanical strains and which could as such be used, for example, as blasting sand or as aggregate in cast concrete, bricks, road surfacing materials, or the like. The object of the invention is, furthermore, to provide a ferrochromium slag which gives such materials strength properties improved over those obtained using the above-mentioned prior known ferrochromium slag.